The present invention relates to corrugating rolls and, more particularly, to a method and apparatus for coating corrugating rolls whereby the rolls are provided with a hardened outer surface for resisting wear.
Corrugating rolls are used in machinery such as single facer or double facer corrugators which are used in the manufacture of corrugated paperboard. The corrugating rolls include a series of flutes formed around the circumference of the roll wherein the flutes are adapted to form corrugations in paper web during the formation of corrugated paperboard. In the manufacture of corrugating rolls, it is necessary to have a hard, wear resistant surface on the roll and the flute shapes and contours of the roll must be produced to close dimensional tolerances. In the manufacture of certain prior art rolls, the rolls were rough machined using ordinary cutting tools and then hardened by conventional heat treatment. The heat treatment tended to distort the machined roll such that a further operation of grinding was required to obtain the final desired dimensions for the flutes on the roll.
In order to extend the roll life, a hard exterior coating was typically applied to the surface of the roll to thereby increase its resistance to wear. Generally, chrome plating has been used to coat the outer surface of corrugating rolls, and such chrome plating has provided the desired result of increasing the life of the roll. However, there are problems associated with the use of chrome plating on rolls including the plating being susceptible to cracking and chipping. Once the surface of the roll has cracks or chips, the wear caused by the sliding of the paper web over the roll greatly increases, such that the useful life of the roll before it is either replaced or reground is significantly shortened.
Accordingly, there is a need for an improved corrugating roll surface which provides increased resistance to surface damage and which further provides an increased service life for the roll.